1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and a computer-readable recording device for detecting, from an image, which is obtained by imaging inside of a subject's body, a region unnecessary for diagnosis.
2. Description of the Related Art
Conventionally, endoscopes have been widely spread as medical observation devices that are introduced inside subjects such as patients and observe noninvasively inside living bodies. In recent years, swallowing type endoscopes (capsule endoscopes) have been developed, which accommodate imaging devices, communication devices, and the like inside capsule-shaped casings and wirelessly transmit image data acquired by capturing images with the imaging devices to outside of bodies.
However, observation and diagnosis of the image (intraluminal image) captured by such a medical observation device inside a lumen of a living body require much experience. Therefore, medical diagnosis support functions for assisting the diagnosis by doctors are desired. As one of image recognition techniques realizing such a function, a technique has been proposed, which is for automatically detecting a region to be noted from an intraluminal image, and extracting and presenting the region to be noted, or on the contrary, excluding the region to be noted from a target to be diagnosed for presentation.
As a method of determining whether a region in an intraluminal image is a region to be noted or not, for example, a method is known, which uses, based on a plurality of images (teacher data) having coordinate information given beforehand on various regions (for example, a mucosa region and a lesion region), a color feature data space having components that are color feature data (for example, G/R values and B/G values) based on pixel values (R-value, G-value, and B-value) of each pixel. In this method, to the color feature data space, for example, a determination threshold value is set between a color feature data distribution of pixels belonging to the region to be noted and a color feature data distribution of pixels belonging to a region other than the region to be noted, and by threshold processing color feature data of each pixel of the intraluminal image to be determined with the determination threshold value, whether or not each pixel belongs to the region to be noted is determined.
However, a range in which various regions are distributed in a color feature data space may largely vary among intraluminal images and thus there is a problem that a detection accuracy in the above described method becomes low. Therefore, in Japanese Laid-open Patent Publication No. 2010-113616, in a color feature data space, by performing clustering on color feature data distribution of pixels of an intraluminal image (or small regions obtained by dividing the intraluminal image), comparing a representative value, such as a centroid, calculated from each cluster, with the above mentioned determination threshold value to determine whether or not each cluster belongs to each region, reduction in a detection accuracy caused by variation in distributions among images is suppressed.